This invention relates to apparatus for automatically engaging of a turning gear to effectively rotate a turbomachine rotor. More specifically, the present invention is directed to apparatus for remotely engaging a turning gear and for providing fail-safe circuitry for assuring appropriate operation.
The necessity of rotating steam turbine rotors at very slow speed following shutdown of the machine is well understood. Any heated rotor which is allowed to stop may become out of round, bow, or develop permanent stresses if not continuously rotated to apply stresses and heating uniformly about the rotor. Conventionally, an electric motor is connected to the turbine shaft through reduction gearing such that the motor may be energized and the gearing engaged to rotate the shaft. The arrangement involving the electric motor and the reduction gearing to provide both motive means and engagement means for placing the gear in contact with the rotor is well known.
At the present time, the general method of engaging turning gears on steam turbines is to manually displace the turning gear to bring it into engagement with a coacting rotor gear. An operator is required to unlatch and pull or push a handle on the turbine and at the same time is required to jog the turning gear until the turning gear engages the coacting rotor gear. Two operators may sometimes be required for this operation.
Turbines are often located in hazardous environments where remote control is desirable. Control from a remote control room would be convenient from an operations perspective also, since it would allow a single individual to effectively engage the turning gear.
Previous turning gear designs permit the operator to engage the turning gear before the rotor is stopped which may result in damage to the rotor and/or failure of the turning gear. The simple mechanical manual engagement provided no preventative limitations which would keep the operator from engaging the turning gear while the rotor was still operating.
Additionally, the turning gear may be utilized to position the rotor when it is desirable to have the rotor in a specific orientation as, for instance, when a specific blade is to be visually inspected. The present turning gear arrangements have the problem that the turning gear does not remain engaged after operation is discontinued. In present designs, the turning gear remains in engagement with the rotor gear as long as the turning gear is being driven to rotate the rotor. Once the turning gear is not driven, the interaction between the gears discontinues and the turning gear returns to its original position out of engagement with the rotor gear. Hence, it is not possible to position the rotor without resetting the turning gear each time the position is to be changed.
The herein described invention concerns a remote control for allowing a single operator in a remote location to simultaneously engage the turning gear and to jog the motor driving the turning gear to allow engagement with the rotor. Additionally, the herein invention provides various interlock means for preventing the turning gear from being engaged to the rotor if the rotor has not stopped. Furthermore, the present invention provides for positive engagement of the turning gear to the rotor such that the turning gear may be utilized to position the rotor for various service requirements without the necessity of repositioning the turning gear each time the rotor position is to be changed.